The morphology, dimensions, aberrations, and ultrastructure of channel catfish (Ictalurus punctatus) spermatozoa were studied. Spermatozoa of a wild catfish stock from Louisiana were compared to those of a domestic stock from Mississippi. The spermatozoon of channel catfish consists of a rounded dark head, a collar-like midpiece, and a long flagellum. The average dimensions were: head length, 2.3 µm; midpiece length, 1.6 µm; midpiece width, 3.1 µm; and flagellum length, 94.9 µm. The flagellum had the classical (2.9 + 2) axoneme. On the average, 4.7% of the spermatozoa in the fish studied were biflagellar. Each flagellum arose from an individual centriolar complex. Domestic fish stock had a higher percentage of normal gametes compared to wild stock.